The Crystal Cavern
by KittyZozo3366
Summary: After spotting a mysterious blue box on the beach, Steven and the Crystal Gems are drawn into an adventure which will reveal a secret hidden beneath Beach City.


Steven was playing on his game console, the Gems away on a mission without him. Suddenly, he heard some strange noise: _Vworp... vworp...vworp..._ Steven looked around the house first, and then he noticed something on the beach: a blue phone booth setting in the sand. Knowing that was the thing that made the noise, he came up to it cautiously. The door to the phone booth opened and a man stepped out, dressed in a dark blue suit with shined, black shoes. He also wore sunglasses, and sighed as he looked across the sunny beach.

"Um..." Steven was taken aback that this man appeared to be human. "Hello."

The man looked down at the young boy, lowering his sunglasses to properly see him. "Hello there. Can I help you?"

"Um...why did you park your...box on the beach?"

"Because the last time I left it at a parking meter, I got a ticket." The man taking a seat on the sand and laying back to relax.

Steven chuckled at the man's joke, but he was ignoring the problem. He exclaimed, "But you're right next to my house! C-Can't you put it somewhere else?"

The man looked up at Steven's house, admiring the large stone statue towering over it. "Nice place."

"Thanks. So, can you move your box...?"

The man sighed and got up. "One second." He headed inside the box and within seconds, it whirred and faded out from sight. Steven watched in awe as it faded out of existence, and then he noticed it reappear further down the beach.

"Whoooooaaaaa!" He ran down the beach to meet the man when he stepped out of the box again. "How does it do that?"

"Disappears in one place, reappears in another. You wouldn't understand," the man replied.

"But the only thing I've seen that works that way is Gem technology!" Those words made the man stop walking back to the beach.

"Excuse me? Gem technology?"

"Y-Yeah." Steven nodded, starting to regret telling this man about the Gems. "The stuff I see on Gem ships and the Temple. Only it works...like that."

The man removed his sunglasses completely. "You've seen this sort of thing before?"

"Yeah. Your phone booth kind of works like a Warp Pad."

The Doctor frowned. "What's your name?"

If this man was a threat to the Gems, he would've made his first attack by now, so Steven answered, "Steven. Steven Universe. What's yours?"

"You can call me the Doctor."

"...That's not really a name."

"Well it's _my_ name," the Doctor replied. "Some would say that Universe isn't really a name."

"It's a surname."

"We're losing track of the real issue: where is this Warp Pad you speak of?"

"Oh, it's in the house." Steven took the Doctor's hand and lead him inside. The Doctor followed the boy in and looked around curiously. "Wait..." Steven stopped as they came inside and looked back nervously at the Doctor. "How can I trust you? I mean, you just showed up out of nowhere and now you're asking about Gem stuff."

"Well, what do we have here?" the Doctor asked to nobody in particular as he saw the Warp Pad. He walked over to it and took out a small device from his pocket. He held it out to the Warp Pad and it whirred. "Organic teleportation technology...commonly used by Petradisapiens. Thousands of years old, but it still looks like it works..."

"You should go-" Suddenly, the Warp Pad activated, and Garnet, Amethyst, and Pearl appeared on it. The three gasped at the seemingly human man right next to it, but the Doctor looked just as astonished.

"Amazing..." he uttered, approaching the Gems, and he walked in a circle around them. "I haven't seen any Petradisapiens on Earth for thousands of years. After the Gem War, I assumed they'd either fled the Earth or died out."

"H-How do you know about the Gem War?" Pearl stammered, nervous that Steven brought a total stranger into the house.

"Because I'm the Doctor. I know everything," he replied. "Pleasure to meet you, Miss..."

"Pearl. And you can't know everything- that's impossible for humans."

"I don't think he's human," Steven stated. "He came in a teleporting blue phone booth."

"A WHAT?"

"It's called a TARDIS, and it's not a 'blue phone booth,' it's a spaceship," the Doctor explained.

"Cool! I wanna see!" Amethyst ran for it, only for Garnet to grab her before she can go any further.

"Amethyst, this man could be dangerous," she warned.

"That's right. Steven, we need to get this man out of the house," Pearl told him.

Steven grabbed the Doctor's arm. "I'm sorry, Doctor, but you can't stay. Take your TARDIS to some other beach, please."

"Trust me, I'm only dangerous to my enemies," the Doctor reassured. "I'm pretty sure none of you are my enemies."

"We could be if you keep searching around the Temple like this," Pearl warned.

"I wasn't searching around. I was just having a nice day at the beach before I met Steven."

She frowned at Steven and he says, "He just appeared out of nowhere! I-I wanted him to move his ship before you guys thought he was a threat."

Amethyst pleaded, "Can't he stay a little while? I really wanna see his ship!"

"Amethyst, you can't go in his ship without his permission," Pearl stated, and then she turned back to the Doctor. "Could we go aboard your ship? For...research."

"Just don't touch anything," the Doctor said.

"Amethyst, don't touch anything," Pearl restated.

"I heard him, P!"

"I'm just making sure." Then, the Crystal Gems followed the Doctor to the TARDIS. He opened the doors, revealing the large interior of the seemingly small phone box.

"Whoa!" Steven exclaimed. "It's like the Rubies' ship!"

"More like the Rubies' Ship is like my TARDIS," the Doctor clarified. "I miss the times when alien ships were more original."

"Wow! This is so cool!" Amethyst giggled as she ran inside.

Pearl asked the Doctor, coming up to him, "And how do you know about the Rubies' ship?"

"Oh, Petradisapiens 'borrowed' our method of making ships dimensionally transcendental. And to think their Government wasn't annoying enough," the Doctor grumbled.

"I know what you mean," Pearl agreed.

"It is rather impressive," Garnet commented.

"I'm glad the two of you agree." The Doctor's reply surprised Garnet. "What? Did you really think I wouldn't notice both of your gemstones?"

"So, how do you know so much about Gems, Doctor?" Pearl asked.

"About as much as I know about all the other alien races in the galaxy."

"And where do you get all this information?"

"I learned it. But I learned most of it during the Gem War."

Amethyst gasped, "No way...YOU WERE IN THE GEM WAR?!"

"I was more like an observer."

Pearl asked. "How could you observe the Gem War without being caught in the crossfire?"

"I'm very stealthy."

"A blue phone booth in Earth 5000 years ago would have stuck out easily."

The Doctor smirked. "And yet I wasn't noticed."

Steven asked, "Did you know any Gems?"

"I never met anyone from the Rebellion, but I did run into a few...OTHER Gems in Colony Ship over the Arctic," the Doctor explained.

"You were at the Arctic Ship?" Garnet asked.

"I visited it once a few thousand years ago. How about you?"

"It was already destroyed by the time we got there."

"Like I said, I only visited it once," the Doctor replied with a knowing smirk.

Garnet smirked back. "I'm starting to like this Doctor."

"Well, it was nice to meet you, Doctor," Pearl stated, "but we would like the Temple to stay a secluded place."

"I know the feeling. Okay, time to go," the Doctor said to everyone in the TARDIS.

"Awww, man…" Amethyst grumbled as they walk out. Pearl, Garnet, and Steven followed her out, Steven giving the Doctor a wave as he goes out, and the Doctor waved back as they head off.

The Crystal Gems then headed back to the Temple, and once they got inside, Steven grabbed Garnet's hand. "Garnet... was the Doctor really there? At the Gem Wars?"

"I don't know, Steven, not for sure, but someone certainly took out that ship before we did. If the Doctor's telling the truth, we could have a potential ally."

Steven smiled. "I think he'd make a good ally. He seems smart."

"Plus, his box is really cool~" Amethyst added.

"Cool box or not, we still don't even know why he came here," Pearl stated.

Steven asked, "Didn't he say he came here to come to the beach?"

Suddenly, a loud rumbling came from the beach. "That doesn't sound good," Garnet commented without losing her monotonous tone. The Crystal Gems drew their weapons and headed outside. The sand on the beach parted as a large, clawed, metallic hand rose from it. The Doctor looked out of the TARDIS and watched as the creature climbed out, sand falling off its shiny body as it revealed itself. It had the appearance of a quadrupedal, corrupted Gem, with some sharp, jagged teeth jutting out of its large mouth- only its body was completely made of metal.

"Well, that's new..." the Doctor gasped.

Pearl also gasped. "What sort of Gem is that?!"

"They can't look like that?" Steven asked.

The metal Gem stomped over to the Crystal Gems; unlike other corrupted Gems, this one moved like it's being controlled. Amethyst shouted, "Come on! Let's shut this tin can down!" Pearl shot some beams from her staff and Steven tried throwing his shield, but neither attacks put a dent in the corrupted Gem's metal exterior.

Steven shouted, "Doctor, help us!"

The Doctor ran in front of the Gems and looked over the corrupted Gem. "I'm guessing you've never encountered this creature before?"

"Not like this. Usually they're like us, but more beastly," Pearl explained, "but this one has an exterior like a car!"

The Doctor continued looking over the metal Gem. "Petradisapien with a corrupted gemstone...but it's been converted."

"Into what?" Garnet asked.

"A Cyberman. Or a CyberGEM in this case." The Doctor shrugged at his own name suggestion.

"Have you dealt with something like this before?" Pearl asked. "What's affecting it?"

"It's what happens to anything that's converted by the Cybermen: they strip it down of anything that made it what it was before, and then add it to their ranks."

Amethyst frowned, finding none of that information helpful. "And how do we stop it, Doc'?!"

"First, never call me that again. And second, I know one that it's scared of the most." The Doctor waved his arms to attract the Cybergem's attention. "Hey, ugly! Forget this lot! I'm the one you want! Why convert a few more Petradisapiens when you could convert a Time Lord?!"

The Cybergem stared at the Doctor, and Steven frowns. "I don't think it'll understand you..."

" _Identify yourself,_ " the Cybergem ordered, its voice deep and robotic, blue light shining from behind its metal teeth as it spoke.

The Doctor smirked. "Go ahead and scan me. Check your records. You'll find me eventually." The Cybergem's head moved up and down as it scanned the Doctor. The other Crystal Gems were too afraid to speak; they'd never dealt with something like this before.

The Cybergem went motionless as it looked through its records, until it finally stated, " _You are the Doctor._ "

"You're damn right, I am," the Doctor replied confidently.

" _You will be deleted._ " The Cybergem raised its metal claw, the palm sparking with electricity.

"MOVE!" The Doctor dived out of the way as the Cybergem slammed down its claw.

The Crystal Gems ran out of the way and Pearl exclaimed, "Your plan was to make them angry!?"

"Of course not! My plan was to-" He dived out of the way as the Cybergem slammed down its claw again. "My plan was to keep it away from you lot."

"Doctor, we're the only ones who know how to deal with these!" Pearl, unfocused with the monster and upset with the Doctor, didn't notice the monster about to slam its claw on her.

Steven pushed her out of the way and for extra measure, bubbles both of them. He argued, "But we don't know what the Cybermen are! We need the Doctor's help, Pearl!"

"Oh, come on! You're smart Petradisapiens! What's one of your main weak points?!" the Doctor asked.

"Our bodies, and if we're corrupted, we're much weaker," Pearl explained. "But this one is covered in armor, so the Cybermen have taken care of any weak point it has!"

Steven paused and looked up at it. "What if we hit the eye?"

"Come on! What else?!" the Doctor called out.

"The Gem?!" Garnet guessed.

"Exactly! The Gem!" The Doctor dodged yet another attack from the Cybergem. "When the Cybermen convert a living being, they leave a small part of the nervous system so they respond like a living being, but a Petradisapien's gem _is_ their nervous system. It's what makes them… _them._ "

"And where is the gem?!" Amethyst called, wrapping her whip around one of the Cybergem's legs to trip it up.

"I don't know! Petradisapiens can position their gems anywhere they choose!"

"But we don't SHATTER GEMS!" Steven yelled, tearing up.

The Doctor looked to Steven with a serious frown. "And neither do I! Look for an access port! It's usually in the chest! All Cybermen have one!"

"Amethyst! Get it on its back!" Pearl ordered.

"Got it!" Amethyst pulled back on her whip, tripping the Cybergem up. She jumped up and pulled the whip again, flipping it onto its back. Garnet grabbed the Cybergem and held it in a headlock. Pearl and Steven saw the access port and opened it using their weapons.

"Steven, catch!" The Doctor tossed him the whirring device he used on the warp pad.

Steven looked at the wand-like device. "What do I do with it!?"

"Climb inside and look for the Gem! When you find it, hold down the button and hold the glowing part against it!"

"Okay..." Steven then climbed inside and saw a lot of wiring amidst other electronic components. Then, he noticed a blue gem at the heart of the technologically-altered monster. Steven put the part that's glowing to the gem and pressed the button. The gem rumbled, seconds before it poofed out of existence. Steven fell towards the beach, the gem in his hands.

"Steven!" Garnet gasped as the Gems went to his aid, and the Doctor followed suit.

Garnet caught him first and he sighed. "Thanks, Garnet." The Doctor snatched the Gem and "wand" from Steven's hands, and used it to scan the Gem. Steven and the Gems saw that even the gem itself had been converted by the Cybermen, engraved with patterns resembling a circuit board, along with computer chips attached to it.

"What if it reforms?" Pearl asked as she studied it.

The Doctor ignored her question as he scanned the converted Gem. "This is just...disgusting."

"Say wut?" Amethyst looked confused.

"I mean, I've seen creatures converted before, but this..." the Doctor sighed. "Just look at it. They took the same process of conversion that they use on humans and altered it so that it could be compatible with Petradisapien gemstones."

"I must admit, it is a perversion of the gem," Pearl agreed, "maybe even worse than corruption."

The Doctor gestured to how the gem cut looked...crooked. "You see that? They lasered off the top layer of the gemstone to add the circuity. That's like peeling off a human's skin to add the wiring."

"That's despicable," Garnet agreed.

"Could...could they do that to us? O-Or to anyone else in Beach City?" Amethyst asked.

Steven worried about all the people who could be turned in Cybermen: Connie, Sadie, Lars, Onion... He then asked, "Do you know where they could be?"

"If the Cybermen are here, then they're bound to be hiding somewhere secure." The Doctor looked to the sand the Cybergem had crawled out of. "Somewhere underground. But before we do anything else..." He removed one of the chips from the Cybergem.

"What are you doing?" Garnet asked, curious.

"I removed the emotional inhibitor," the Doctor replied. "It's the least I could do for it."

"Do you think we can bubble it like this?" Steven asked.

"You can try." The Doctor handed it to Steven, and somehow, he managed to bubble it. He sighed in relief and sent it off to the Temple.

Amethyst asked, "What did that emotion...thingy even do?"

"The Cybermen don't want their converted allies to feel emotions, so the inhibitor makes them numb. If they were to see themselves as Cybercreatures...if they could see what had been done to them...they'd go insane."

"We need to find them," Steven said sternly.

"Does anyone know if there are any underground tunnels where the Cybermen could be hiding?" the Doctor asked, knowing the Gems knew Beach City better than he did.

"There are caves, but...they're underneath the Temple. The only way to access them is through the Temple itself or to brute force your way down there," Pearl explained.

The Doctor gestured to the TARDIS. "Or we can take my ride."

"Shotgun!" Amethyst shouted.

"Um, is this going to be a safe ride?" Pearl asked.

"As safe as it can be." The Doctor walked to the TARDIS and the Crystal Gems followed. They headed inside the TARDIS and the Doctor started working the controls.

Pearl looked over the controls curiously. "These look...complicated."

"They're really not," the Doctor stated as he works them with ease.

Soon, the TARDIS started up, shaking around, and the Gems held onto the railing, surprised by the shaky ride. "Woooh! It's like a ride at Fun Land!" Amethyst whooped. The TARDIS soon came to a stop, and the shaking ceased.

Pearl looked shaken by the ride, more than the others. "I-I didn't think such an impressive vehicle would be so...shaky."

"Yeah, it's originally designed to have six pilots," the Doctor replied as he headed for the door. "Come on now. We've got work to do." The Crystal Gems followed him out into the caves. The cave walls deep beneath the temple appeared to be constructed from sandstone, but what caught the group's attention were the large wires and tubes connected to the walls. "I see they made themselves comfortable down here," the Doctor commented.

"But how long have they been down here?" Pearl asked. "These creatures seem to like their presence to be known, so they wouldn't be discreet about digging or hiding themselves."

"That depends on how secretive they want to be." The Doctor looked over the wires, even going so far as to lick the metal. "That's new. Put in place about...five days ago."

"So they've been here a week at least and we haven't known about it?!" Pearl exclaimed.

"It seems so."

Pearl tried not to lose it right then and there, but Steven calmed her by saying, "Pearl, th-they haven't conquered the world yet. There's still time for us to stop them."

"If we follow the wires, they should lead us to a power source," Garnet added.

"Then what are we waiting for?" The Doctor set off down the tunnels. The Crystal Gems followed the Doctor and the wires, their Gems lighting the way, but they also watched for any signs that something might come from anywhere else.

As they walked, Amethyst asked, "Hey, Doctor, what do we do when we find the Cyberguys? Do we mash 'em up~?"

"I think that would be best, especially if they're targeting Gems and maybe even humans," Pearl replied.

"Doctor, is there any way that the converted Gems can be restored?" Garnet asked.

"I'm afraid not," the Doctor sighed. "Once a species is converted, there's no way of reversing it."

Steven frowned. "Then we need to stop them before they convert more."

"I thought that was already the plan," the Doctor retorted.

"Do you even have a plan?" Garnet asked.

"I do, but for it to work, you need to trust me."

Pearl asked, "Maybe you could tell us what you have planned?"

"Not yet, but it has something to do with this." The Doctor reached into his coat and took out a small flash drive.

"Do they have computers?" Steven asked.

"They're Cybermen. Of course they have computers."

"It's just... this looks like a flash drive I'd stick into my laptop."

"I know what I'm doing, Steven," the Doctor insisted. The Gems stopped in their tracks when they find their path blocked by a lone Cyberman.

"Doctor, what do we do?" Pearl kept a firm grip on her staff.

"Stand down." The Doctor stepped forward with his hands raised. "You do not need to harm us. We're not going to retaliate."

" _You are the Doctor. You are our enemy. You will be deleted,_ " the Cyberman stated. The Gems heard loud, metallic thuds behind them, and they turned around to see two more Cybermen blocking their way out.

"No. You're going to covert me."

Garnet exclaimed, "What are you doing?!"

"Doctor, you don't have to do this," Steven pleaded.

" _You lie. Why would you willingly surrender to us?_ " the Cyberman asked, also doubtful.

"Because I'm willing to make an offer," the Doctor said. "If you convert me, that's the end of it. You won't have to convert anymore species."

" _Explain_."

"Just think about it: I'll be the first Time Lord to be converted into a Cyberman. You would gain all my knowledge, all my battle experience, my resilience. With me, you won't need any more soldiers."

The Cybermen paused as they consider this offer, and then they asked, " _And what of your allies?_ "

"You leave them be. They won't fight back. Right?" the Doctor looked back at the Gems.

"R-Right." Pearl nodded and put away her weapon. Steven lowered his shield, but kept it out.

"Okay," Amethyst replied with a sad expression, putting her whip away. Garnet stayed silent, but made her gauntlets disappear.

" _The agreement is confirmed. You will come with us,_ " the Cyberman ordered.

The Doctor reminded the Cybermen, "The deal was to let them go."

" _They will be released once you have been converted. You will come with us._ " All of the Cybermen led the Doctor and Gems down the tunnel. The Gems feared what would happen if they disobeyed the Cybermen, so they followed.

" _Guys, do you really trust the Doctor about this?_ " Steven whispered.

" _He's faced these things before,_ " Pearl replied, " _or at least knows what they are. He should know how to deal with them._ "

" _And if he doesn't, we turn 'em into scrap metal_ ," Amethyst whispered back.

The Cybermen took the Doctor over to the operating table, where he's held down with automated restraints. Pearl sighed and turned away, putting her hands over her eyes. "I can't watch..."

" _Begin the conversion_ ," one of the Cybermen ordered. Another Cyberman pressed some controls on computer beside the operating table, and the Gems watched a horrific device lower from the ceiling. It looked like an operating machine that a mad scientist would use- with drills, claws, and other sharp tools attached. Steven turned away as well.

"WAIT!" the Doctor exclaimed, causing Pearl and Steven to look back at him. "You can't do this!"

The Cybermen cornered the Gems and the Doctor sternly. The Gems even saw a total of four Cybergems enter the cave as a means of blocking their escape. " _What is the meaning of this?_ " one of the Cybermen asked.

"You can't do this. Not without the device in my left pocket." The Cyberman reached into the pocket and took out the flash drive. Steven gave a small smirk as he saw it, but stayed quiet.

The Cyberman asked, " _What is this device for?_ "

"It contains a complex diagram of a Time Lord's biological layout. Since I'm the first Time Lord to ever be converted, I figured you would need it. You wouldn't want to shred me up for nothing, would you?"

" _This is correct._ " The Cyberman walked over to the computer and inserted the flash drive. The file was then uploaded. " _Conversion preparations complete._ "

" _Activating conversion process_ ," another Cyberman said, pulling a lever beside the operating table. The second he did so, sparks flew from the computer, the lights around the cave flickered, and the Cybergems writhed and cried out.

The Gems all jumped as the Cybergems cried in pain. Steven yelled, "Doctor! Why are you hurting them?!"

"I'm not hurting them! I shut off their emotional inhibitors!" the Doctor said as his restraints deactivated, and then he quickly climbed out off the table. "And they're not happy!" The Cybergems snarled and lunged at the Cybermen before tearing them apart.

Pearl took out her weapon. "I'm actually thankful they're not attacking us!" Garnet summoned her gauntlets and went for one of the Cybergems, prying at its chestplate. Amethyst used her whip to trip one of them up. Pearl pried open the chestplate of the one that Amethyst toppled, and Steven hit his shield against one to knock it down. The Doctor climbed on top of the remaining Cybergem and used his sonic screwdriver to remove the chestplate. The Crystal Gems helped take down the last Cybergem with him, and now, the cave was a mess, filled with totaled Cybermen and poofed Cybergems. The Crystal Gems picked up the Cybergems'...gems and bubbled them. The Doctor sighed as he looked around the cave.

"Will more Cybermen come?" Pearl asked.

"Not likely. Judging by the size of this base, I believe that was the lot of them."

"I guess you'll be leaving then?"

"Well, my work here is done, but I still need to bring you up to the surface."

Steven snickered. "Maybe that's why the Cybermen were so grumpy: they were stuck down here."

The Doctor smirked. "I guess we'll never know." They all headed back to the TARDIS.

After another shaky ride in the TARDIS, the Crystal Gems got out. Steven looked back to the Doctor and asked, "Will we ever see you again?"

"Who knows? Maybe I'll come back to check on you from time to time," he replied.

"It was certainly a pleasure meeting you." Garnet smiled.

"Yeah, haha! You were awesome~!" Amethyst said.

"I must admit, you seem like a very capable and smart ally," Pearl agreed.

"As do the four of you," the Doctor smiled. "I'm sure you'll do a good job of keeping the Earth safe while I'm gone."

Pearl smiled as well. "Of course!"

"Well, good luck. I'll be on my way."

"See ya around, Doc'!" Amethyst waved before he closes the TARDIS doors.

"Amethyst, stop calling him that." Pearl frowned. The Gems watched as the TARDIS faded out of existence, leaving a square in the sand where it had rested.


End file.
